. A manual of zoology. 472 MANUAL OF ZOOLOGY nil Following the tibio-tarsus is an elongated bone, the tarso- metatarsus (is. intts), presenting at its proximal end a con- cave surface for the tibio-tarsus, and at its distal end three distinct pulleys for the articulation of the three forwardly directed toes. In the young bird the proximal end of this bone is a separate cartilage (Fig. 2S5, tl'1), repre- senting the distal tarsals, and followed by three distinct metatarsals, belonging respectively to the second, third, and fourth digits. To the inner or preaxial side of the tarso-metatarsus, ne
. A manual of zoology. 472 MANUAL OF ZOOLOGY nil Following the tibio-tarsus is an elongated bone, the tarso- metatarsus (is. intts), presenting at its proximal end a con- cave surface for the tibio-tarsus, and at its distal end three distinct pulleys for the articulation of the three forwardly directed toes. In the young bird the proximal end of this bone is a separate cartilage (Fig. 2S5, tl'1), repre- senting the distal tarsals, and followed by three distinct metatarsals, belonging respectively to the second, third, and fourth digits. To the inner or preaxial side of the tarso-metatarsus, near its distal end, is attached by fibrous tissue a small irregular bone, the first metatarsal (intts. 1). The back- wardly directed hallux has two pha- langes, the second or inner toe three, the third or middle toe four, and the fourth or outer toe five. In. all four digits the distal or ungual phalanx is pointed and curved, and serves for the support of the horny claw. A further peculiarity is the fact that the larger proportion of the bones contain no marrow, but are filled during life with air, and are therefore said to be pneumatic. The cavities of the various bones open externally in the dried skeleton by apertures called pneumatic foramina (Fig. 281, pn. for), by which, in the entire bird, they communicate with the air-sacs (vide infra). As might naturally be expected, the muscles of the fore- limb are greatly modified. The powerful downstroke of the. Fig. 285. — Columba livia. Pan of left foot of an un- matched embryo (magni- fied). The cartilage is dotted. mtl. 2, second; ;;///. ?, third; and mtl. 4, fourth metatarsal; //.tibia; //. /, proximal tarsal car- tilage; //. .?, distal tarsal cartilage. (From Parker's Zootomy.'). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Parker, T. Jeffery (Thomas J
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